Diabetic patients are at increased risk of morbidity mostly through the development of atherothrombotic vascular disease. Platelet hyperactivity and endothelial cell damage in type I diabetes suggest the hypothesis that in diabetes there is an increased potential for thrombus formation. To test this hypothesis and delineate the receptor(s)-ligand(s) participating, the investigators propose to use a recently developed analytical method based on real time confocal videomicroscopy. By using different immobilized ligands, such as von Willebrand Factor (vWF), fibrinogen, collagen type I, and subendothelial matrix, and by using various monoclonal antibodies that specifically block the functions of platelet glycoprotein (GP) Ib and integrin aIIbB3, and using a novel method based on fluorescent beads coated with GPIba recombinant fragment, the specific changes in receptor-ligand interactions in type I diabetes will be established. Secondly, they will probe the thrombogenicity of endothelial cells in diabetes using human umbilical vein endothelial cells (HUVEC) grown under elevated glucose levels. These endothelial cells, or their subendothelial matrices, will be placed in the flow chamber and thrombus formation over them be analyzed by real time confocal videomicroscopy under relevant flow conditions.